In a medium bowl set over a saucepan of simmering water, whisk the egg yolks and sugar until frothy and registers 140 degrees F on a thermometer, about 8 minutes. Set aside to cool. Whisk in the mascarpone.
Whip the heavy cream until stiff peaks form. Fold 1/3 into the egg mixture. Fold in the remaining whipped cream.
Working 1 at a time, quickly dip the bottom half of 10 ladyfingers in the espresso until just absorbed. Arrange the soaked ladyfingers in the bottom of a 9-inch springform pan. Spread half the mascarpone mixture over the ladyfingers. Repeat the soaking process with the remaining 10 ladyfingers and arrange over the mascarpone. Spread the remaining mascarpone over the ladyfingers and cover with plastic wrap. Refrigerate the tiramisu at least 3 hours and up to overnight. Just before serving, dust with cocoa powder.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.